KR20210130120A - The Manufacturing Method of the Nitride Semiconductor Device - Google Patents

Abstract

The present invention relates to a method of manufacturing a nitride semiconductor device that includes a nitride thin film layer forming step of forming a nitride thin film layer on a substrate; and a photoelectrochemical etching step of forming a nanograting structure by performing photoelectrochemical (PEC) etching on the nitride thin film layer. According to the present invention, when the surface pattern of a semiconductor substrate thin film layer is formed, photoelectrochemical etching is performed to form a nanograting structure. So, a three-dimensional pattern can be formed in an inexpensive and simple process. A nanopattern is formed through a single process to reduce the refractive index of the pattern. There is an effect of realizing high light extraction efficiency.

Description

The manufacturing method of the nitride semiconductor device TECHNICAL FIELD

The present invention relates to a method for manufacturing a nitride semiconductor device, and by performing photoelectrochemical etching when forming a surface pattern of a semiconductor substrate thin film layer to form a nano grating structure, a three-dimensional pattern can be formed in an inexpensive and simple process, and The present invention relates to a method of manufacturing a nitride semiconductor device capable of reducing a refractive index of a pattern by forming a nanopattern through a process and realizing a high light extraction efficiency.

The present invention is a university ICT research center support project of the Ministry of Science and ICT and the Information and Communication Planning and Evaluation Institute [task management number: 1711093073, task name: development of smart engineering technology for strengthening the manufacturing technology innovation capacity of small and medium-sized enterprises], the Ministry of Trade, Industry and Energy and Korea Industry Derived from research conducted as part of the Ultra-Power Saving LED Convergence Technology Development-Micro LED Convergence Technology Development Project [Project Management Number: 20004550, Project Title: Development of Nano Hole Air Adsorption Method Mass Transfer Technology for UHD Class Micro LED Display] of the Korea Institute of Technology Promotion it has become

Light emitting diodes are applied to backlight light sources, display light sources, general light sources, and full-color displays. As a material of such an LED, group III-V nitride semiconductors such as GaN (Gallium Nitride), AlN (Aluminum Nitride), InN (Indium Nitride), etc. are known.

Group III nitrides, including GaN, form a p/n junction by S.Nakamura and emit blue light. It is widely applied to high-power electronic devices. The fabrication of these devices requires the growth of various high-quality nitrides such as AlGaN and InGaN, as well as p-type and n-type GaN. this is being used

However, in order to make a suitable device structure along with the growth of a good thin film, a process of etching the thin film into a desired shape and forming electrical and optical contact there must be followed. Therefore, in order to form an appropriate device structure, etching of a thin film grown or deposited on a substrate is essential. As a method for etching these thin films, a chemical etching method using an etching solution and a dry etching method using plasma may be used, and these methods are widely used for etching devices using materials such as Si or GaAs.

However, Group III nitride semiconductors, including GaN, are chemically very stable, so they use high-density plasma such as ICP (Inductive Coupled Plasma), ECR (Electron Cyclotron Resonance), or CAIBE (Chemically Assisted Ion Beam Etching) using high-energy ion beams. ) is effectively etched by dry etching methods such as However, all of these methods require expensive equipment, damage due to particle collision on the etched surface, and have limitations in implementing a high selectivity with an etch mask.

Therefore, a chemical etching method is required as a more useful method for etching a group III nitride such as GaN. These are very stable and are not etched with an easily accessible etching solution.

As a prior art related to the etching of group III nitride, Minsky et al. ['Room temperature photoenhanced wet etching of GaN; Appl. Phys. Lett; Vol.68, No.11; pp.1531-1533; 1996.3].

In this paper, Minsky et al. confirmed the etching of n-GaN by the photoelectrochemical method, which is a chemical etching method with light assistance. This causes holes to be created in the substrate through irradiation of short-wavelength light such as Ultra Violet, and these holes help the oxidation reaction of the substrate, so that the etching of group III nitrides with low reactivity proceeds effectively. In such an etching method, by allowing unnecessary electrons among photogenerated carriers in the substrate for etching to escape from the substrate quickly, recombination of the photogenerated holes is suppressed so that more holes can contribute to the etching. In this etching method, it was possible to obtain an etching rate of several hundred Å/min or more and several thousand Å/min for n-GaN, and the characteristic of selectively etching n-GaN with respect to p-GaN that cannot be etched using KOH solution was excellent. was also confirmed.

Other prior art related to group III nitride etching include C. Yotsey's paper ['Dopant-selective photoenhanced wet etching of GaN'; J. of Electronic Material; Vol.27, No.4; pp.282-287; 1998].

This paper describes the dopant-selective photoenhanced wet etching process for GaN. A KOH solution was used for the etching process, and in order to obtain the properties of selectively etching for intrinsic and p-type GaN, light was irradiated with an Hg arc light source and tested. The p-, i-, and n-type GaN substrates used for etching were grown on a 6H-SiC substrate by MOCVD. During the etching for minutes, a constant photo-current of about 2 μm flowed during the etching process of N-type GaN. However, in GaN having an n-i structure, current flows during the etching process of the n-layer, but the amount of current is greatly reduced in the region of the i-layer. In addition, in the p-type GaN, no current flowed and the etching proceeded in proportion to the amount of current. In the case of etching the pn-structured GaN, when the p-layer was removed by dry etching using some CAIBE and then photo-electrochemical etching was performed, the p-layer was not etched but only the n-layer was selectively etched. In this paper, the selective etching characteristics of GaN according to doping were confirmed.

According to this conventional method, the irradiation of light effectively increases the etching efficiency of the n-type material. However, in the case of the p-type material, the bending of the energy band on the surface of the substrate in contact with the etching solution appears to form a potential well for electrons, so holes that promote the reaction do not accumulate and thus do not contribute to the etching. The etching of GaN has never been attempted.

In addition, the method for controlling the etching rate of n-GaN also had difficulties such as changing the concentration of the etching solution or changing the intensity of light. The difficulty in effectively controlling the etching of p-GaN and the etching rate as described above has a problem in that a chemical etching method is used to form a device structure, and there are many limitations.

Korean Patent Registration No. 10-155914 (Registration Date 2019.08.23.) Korean Patent Registration No. 10-2011147 (Registration Date 2019.08.08.)

An object of the present invention is to form a nano-grating structure by performing photoelectrochemical etching when forming a surface pattern of a thin film layer on a semiconductor substrate, so that a three-dimensional pattern can be formed by an inexpensive and simple process, and a nanopattern is formed through a single process. To provide a nitride semiconductor device capable of reducing the refractive index of a pattern and realizing high light extraction efficiency.

In order to achieve this object, a nitride semiconductor device manufacturing method according to the present invention includes a nitride thin film layer forming step of forming a nitride thin film layer on a substrate; and a photoelectrochemical etching step of forming a nano-grating structure by performing photoelectrochemical (PEC) etching on the nitride thin film layer.

The nitride thin film layer may be formed of a group III nitride semiconductor layer.

The photoelectrochemical (PEC) etching may be performed by a wet etching method.

The photoelectrochemical (PEC) etching step may further include changing an angle of incident light during etching.

The photoelectrochemical (PEC) etching step may be performed by applying a current density of 1 to 30 mA/mm 2 to the nitride thin film layer.

The photoelectrochemical (PEC) etching step may be performed by irradiating light in a wavelength range of 200 to 400 nm to the nitride thin film layer.

The photoelectrochemical (PEC) etching step may be performed for a process time of 10 to 60 minutes.

The photoelectrochemical (PEC) etching step may be performed so that the surface of the nitride thin film layer is formed in an etching pattern having a period of 100 to 1000 nm.

In the nitride semiconductor device manufacturing method according to the present invention, a three-dimensional pattern can be formed in an inexpensive and simple process by performing photoelectrochemical etching to form a nano-grating structure when forming a surface pattern of a semiconductor substrate thin film layer, and through one process By forming a nanopattern, the refractive index of the pattern can be reduced, and high light extraction efficiency can be realized.

1 is a schematic diagram illustrating a photoelectrochemical (PEC) etching apparatus that can be used in a method for manufacturing a nitride semiconductor device according to an embodiment of the present invention.
2 to 17 are scanning electron microscope (SEM) photographs showing the surface shape of a thin film having a grating structure formed by the method for manufacturing a nitride semiconductor device according to Examples 1 to 16 of the present invention.
18 is a schematic diagram illustrating a state in which a nitride thin film layer is formed on a substrate that can be used in a method for manufacturing a nitride semiconductor device according to an embodiment of the present invention.
19 is a scanning electron microscope (SEM) photograph showing the surface shape of a nitride thin film layer whose surface is etched by the method for manufacturing a nitride semiconductor device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, in describing the embodiments of the present invention, specific numerical values are merely examples.

1 is a schematic diagram illustrating a photoelectrochemical (PEC) etching apparatus that can be used in a method for manufacturing a nitride semiconductor device according to an embodiment of the present invention, and FIGS. 2 to 17 show an embodiment of the present invention A scanning electron microscope (SEM) photograph showing a surface shape of a thin film having a grating structure formed by the method for manufacturing a nitride semiconductor device according to 1 to 16 is disclosed, and FIG. 18 is a method for manufacturing a nitride semiconductor device according to an embodiment of the present invention. A schematic diagram showing a state in which a nitride thin film layer is formed on a substrate that can be used is shown.

19 is a scanning electron microscope (SEM) photograph showing the surface shape of the nitride thin film layer whose surface has been etched by the method for manufacturing a nitride semiconductor device according to an embodiment of the present invention.

Referring to these drawings, the nitride semiconductor device manufacturing method according to the present invention includes a nitride thin film layer forming step of forming a nitride thin film layer on a substrate; and a photoelectrochemical etching step of forming a nano-grating structure by performing photoelectrochemical (PEC) etching on the nitride thin film layer.

That is, the method for manufacturing a nitride semiconductor device according to the present invention performs photoelectrochemical etching (PEC) by controlling process conditions when forming a surface pattern of a thin film layer of a semiconductor substrate to form a nano-grating structure, thereby reducing the cost of a three-dimensional pattern. And it can be formed by a simple process, the refractive index of the pattern can be relaxed by forming a nano-pattern through one process, and high light extraction efficiency can be realized.

The nitride thin film layer may be formed of a group III nitride semiconductor layer. Group III refers to a semiconductor compound formed by a group III element on the periodic table and nitrogen. As an example of such a ² group element, aluminum (Al), gallium (Ga), indium (In), etc. may be exemplified, and these may include alone or a combination of two or more thereof. Accordingly, it may include GaN, AiN, InN, AlGaN, AlInN, GaInN, AlInGaN, and the like.

The nitride thin film layer forming step may be performed by growing a III-nitride thin film layer, which is an epitaxial layer, on a substrate. In this case, the substrate may be used without particular limitation as long as it is a substrate suitable for growth of a non-polar or semi-polar group III nitride layer. Such a substrate may comprise a symmetrically equivalent surface, such as an a-plane, an r-plane, or an m-plane in the broadest sense.

It is preferable to use an m-plane sapphire substrate in order to realize semi-polarity as the substrate. Prior to forming the nitride layer on such a substrate, optionally removing residual oxygen in the reaction zone, annealing or heat treating the reaction zone using hydrogen and/or nitrogen (eg, high temperature to a growth temperature), etc. can be done Also, for example, in the case of a sapphire substrate, the method may include nitriding the surface of the substrate using anhydrous ammonia or the like.

In addition, prior to growing the group III nitride thin film layer on the substrate, an intermediate layer or a buffer layer may be formed. This intermediate layer is selectively introduced in order to obtain better properties of the group III nitride thin film layer. Exemplary materials are suitable for promoting the growth of not only III-V compounds such as AlN and AlGaN but also non-polar, particularly semi-polar, group III nitride layers. It may be of a different material. In this case, a deposition or layer growth technique widely known in the art, such as MOCVD, HVPE, etc. is utilized. A non-polar or semi-polar group III nitride layer can be formed on a substrate (or an intermediate layer on a substrate) using a conventional layer growth technique, for example, MOCVD, HVPE, MBE, etc., but in order to secure a better quality mold, MOCVD It is preferable to use

The dimension of the selectively introduced intermediate layer is not particularly limited, and for example, may be in the range of at least about 10 to 50 nm. In addition, process conditions may be adjusted to about 550 to 750° C. under atmospheric pressure to form the intermediate layer.

The Group III nitride thin film layer may be formed to a thickness of, for example, about 1 to 10 μm, more specifically, about 2 to 5 μm. In order to form the Group III nitride thin film layer as described above, for example, a growth reaction may be performed for about 60 to 300 minutes under a temperature of about 800 to 1100° C. and a pressure of about 200 to 500 torr.

The photoelectrochemical (PEC) etching may be performed by a wet etching method. A photoelectrochemical reaction is a reaction involving light in the electrochemical system, and although a photoelectrode reaction and a photogalvanic reaction are representative reactions, electroluminescence in which light is generated as a result of an electrochemical reaction is also included.

Semiconductors have a specific energy bandgap. In addition, when a semiconductor absorbs energy greater than its intrinsic energy bandgap, an electron-hole pair is generated. The electrons in the valence band are excited into the conduction band, and a hole is generated in its place. Due to the characteristics of the semiconductor (equilibrium at the fermi level), band bending occurs on the surface of the semiconductor. In the case of an n-type semiconductor, holes move toward the boundary, and in the p-type semiconductor, electrons move toward the boundary.

When explaining the photoelectrochemical etching method in relation to the characteristics of these semiconductors, when a semiconductor is placed in a tank containing potassium hydroxide (KOH) as an electrolyte and irradiated with a predetermined light energy, an electron-hole pair is generated, but the electrons are separated It flows into a counter electrode connected by a lead wire of Since the oxide film is neutralized by potassium hydroxide (KOH), which is an electrolyte, photoelectrochemical etching in which the surface of the semiconductor is etched is possible. That is, a photoelectrochemical etching method is a method of making an electric-hole pair using light (light), neutralizing the generated oxide film and etching it.

The photoelectrochemical (PEC) etching step may further include changing an angle of incident light during etching.

For example, an n-type layer, a p-type layer, and a group III semiconductor layer comprising an active region grown on a substrate may cause light originating from the active region to be large compared to the critical angle for total internal reflection (TIR). may be incident on the sidewalls of the semiconductor layer at an angle of incidence, such that the sidewall reflects more total internally through guided modes towards the top surface of the semiconductor device, and thus the total internally reflected guided modes are critical. More can be incident on the upper surface of the semiconductor layer within the angle.

The photoelectrochemical etching step may be performed by forming a pattern mask (or a protective layer such as a thin film for selective etching) on the nitride thin film layer. The mask of the pattern may typically be made of a dielectric material, for example, SiO2, Si3N4, or the like.

In order to form the pattern mask, an insulating layer is first formed by, for example, plasma enhanced chemical vapor deposition (PECVD). Then, a set of parallel stripe patterns on the group III nitride thin film layer using a conventional photolithography method (in the above method, a conventional method such as ICP-RIE can be adopted for etching, for example) (130) is left. In this case, the region between the masks of the stripe pattern may be referred to as a “window region”.

The width of the mask may be, for example, about 2 to 50 μm (specifically, about 2 to 10 μm), and the width of the window may be set in the range of about 2 to 20 μm (more specifically, about 2 to 10 μm). have. Also, the mask may be suitable if it is in the range of about 500 to 2000 Å thick.

Meanwhile, in the photoelectrochemical (PEC) etching step, a current density that may be generated by a voltage applied to the nitride thin film layer may be set, for example, in a current density range of 1 to 30 mA/mm 2 . In addition, in the photoelectrochemical (PEC) etching step, the process of irradiating light energy to the nitride thin film layer may be performed by, for example, irradiating light set in a wavelength range of 200 to 400 nm to the nitride thin film layer.

In addition, the photoelectrochemical (PEC) etching step may be performed for a process time of, for example, 10 to 60 minutes in consideration of the physical and chemical properties of the nitride thin film layer and the etching electrolyte used, preferably 1 It may be performed for a period of time within an hour.

In the photoelectrochemical (PEC) etching step, etching may be performed on the nitride thin film layer to have a pattern of a specific shape in a self-styled region other than the passivation layer. Here, the surface of the nitride thin film layer may be etched to form an etch pattern having a period of preferably 100 to 1000 nm.

<Example>

Hereinafter, a method for manufacturing a nitride semiconductor device according to the present invention will be described through examples.

A photoelectrochemical (PEC) etching was performed using the epitaxial structure as shown in FIG. 18 . That is, Epi is formed by forming a GaN-based (p-GaN layer: 700-800 nm) nitride thin film layer (multilayer structure using GaN, InN, AlN, InGaN, AlGaN) with a thin film thickness of about 6 μm on a sapphire substrate, and the table below A nano-grating structure was formed on the GaN thin film layer by performing photoelectrochemical (PEC) etching under the same conditions as in Example 1 (Examples 1 to 16). In order to form the nano-grating structure, a predetermined direction was determined to have a constant directionality when the current was injected, and the etching was performed after the current injection. Table 1 shows the injection voltage (V) applied to the photoelectrochemical (PEC) etching step of the method for manufacturing a nitride semiconductor device, the etching time (min), and the etching electrolyte (DI water, KOH) for each example (Example) 1 to 16) numerical values are disclosed. At this time, the photoelectrochemical (PEC) etching process applied to Examples 1 to 16 was set to a temperature of 27° C. and a pressure of 1 atm, and the wavelength range of the UV-LED was set to 200 to 400 nm.

[Table 1]

SEM images of the nano-grating structures generated by the photoelectrochemical (PEC) etching process of the GaN thin film layers of Examples 1 to 16 performed as described above are shown in FIGS. 2 to 17 . As can be seen in FIGS. 2 to 17, the etching patterns of the GaN thin film layers of Examples 2, 4, 6, and 8 using the KOH etching electrolyte under the same injection voltage condition are more clearly generated. it can be confirmed that

As described above, the present invention has been described with specific matters such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , various modifications and variations are possible from these descriptions by those of ordinary skill in the art to which the present invention pertains.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (8)

A nitride thin film layer forming step of forming a nitride thin film layer on a substrate; and
a photoelectrochemical etching step of forming a nano-grating structure by performing photoelectrochemical (PEC) etching on the nitride thin film layer;
A nitride semiconductor device manufacturing method comprising a.
According to claim 1,
The nitride thin film layer is a nitride semiconductor device manufacturing method formed of a III-nitride semiconductor layer.
According to claim 1,
The photoelectrochemical (PEC) etching is a nitride semiconductor device manufacturing method performed by a wet etching method.
According to claim 1,
The photoelectrochemical (PEC) etching step further includes changing an angle of incident light during etching.
The method of claim 1
The photoelectrochemical (PEC) etching step is performed by applying a current density of 1 to 30 mA/mm2 to the nitride thin film layer.
The method of claim 1
The photoelectrochemical (PEC) etching step is performed by irradiating light in a wavelength range of 200 to 400 nm to the nitride thin film layer.
The method of claim 1
The photoelectrochemical (PEC) etching step is a nitride semiconductor device manufacturing method performed for a process time of 10 to 60 minutes.
The method of claim 1
The photoelectrochemical (PEC) etching step is performed so that the surface of the nitride thin film layer is formed in an etching pattern having a period of 100 to 1000 nm.

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